Complete the account of how genes move between prokaryotes.
Prokaryotes pass genes to their offspring ______, but they also exchange them ______ between unrelated cells. This is why ______ resistance can spread across species boundaries, and why the earliest part of the tree of life is better drawn as a ______.
Word bank: vertically · horizontally · antibiotic · web · randomly
Hints
- One direction is parent to offspring; the other crosses between contemporaries.
- Sideways transfer between unrelated lineages breaks the branching structure of a tree.
Show the answer
Prokaryotes pass genes to their offspring vertically, but they also exchange them horizontally between unrelated cells. This is why antibiotic resistance can spread across species boundaries, and why the earliest part of the tree of life is better drawn as a web.
Vertical transfer builds a tree; horizontal transfer draws lines across it, producing a web. This is not a minor complication, it is why antibiotic resistance genes travel so readily between species that never interbreed.
Practise The First Cells and Endosymbiosis
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